Retarder control system



May 4, 1965 Y J. M. BERILL RETARDER CONTROL SYSTEM 6 Sheets-Sheet I Filed Feb. 21. 1958 Hmmpnag/1 mz 620M490 fluzzsfr y 6 J; M. BERILL 3,182,188

RETARDER CONTROL SYSTEM Fil ed Feb. 21, 1958 1 s Sheets-Sheet 2 PM 4 A my 1b.

INVENTOR. dbseph M fle a'll.

BY f 4W8 HIS Amz'om May 4, 1965 Filed Feb. 21. 1958 J. M. BERILL 3,182,188

RETARDER CONTROL SYSTEM 6 Sheets-Sheet 3 1- 2.4T F2571! M212 1: R YB lzm Am? 15 m a a? a 1m 145012 I U lg m BIB y 1965 J; M. BERILL 3,182,188

RETARDER CONTROL SYSTEM Filed Feb. 21, 1958 s Sfieets-Sheet 4 V RETARDER CONTROL SYSTEM Filed Feb. 21, 1958 P268112 1-2qe2w 6 Sheets-Sheet 5 Men ZZTP

N 22 (51260021 2am 2am I I iGRZ FSU 3,182,188 RETARDER @ONTROL SYTEM loseph M. Berill, Edgewood, la., assignor to Westinghouse Air Eralre Company, 'Wilmerding, la., a corporation of Pennsylvania Filed Feb. 21, 1958, Ser. No. 716,752

' 9 Claims. (Cl. 246-182) This invention relates to control apparatus for car retarders, and in particular to an improved control system for multiple section car retarders.

In copending application Serial No. 676,730, filed August 7, 1957, by David P. Fitzsimmons and William A. Robison, Jr. for Automatic Control System for Railway Classification Yards, which is assigned to the assignee of my present application, a system is disclosed for automatically routing cuts of one or more cars to selected storage track destinations, while at the same time controlling the speed at which they couple with preceding cars on the storage tracks to prevent damage to lading.

In a system of the kind disclosed in the above-mentioned, copending application, the rate at which cars can be humped is a major economic consideration. This rate is determined to a large extent by the spacing between cuts of cars having different routes. It would be desirable to limit this spacing to the minimum distance required for proper operation of the switches. However, the separation distance must be at least as great as the longest route section which cannot be simultaneously occupied by two outs. In a classification yard of the type disclosed in the above copending application, the various car retarders located along the routes of the cars will ordinarily have lengths considerably in excess of the minimum required length for the detector track sections employed. It is an object of my invention to provide an automatic control system for such retarders with which the several sections of each retarder can be independently controlled, so that a plurality 'of cuts having ditierent destinations, weights and/ or rollingcharacteristics can simultaneously occupy the same retarder. These independent control sections can be made the same length as, or shorter than, the detector track sections. Accordingly, the over-all length of the retarders will not affect the minimum cut spacing required for the operation of the yard.

It is a further object of my invention to provide a control system for multiple section retarders 'in which each section occupied by a cut is controlled in accordance with the characteristics of the cut to bring its speed to a desired leaving value, and in which, as each retarder section is vacated by a cut, the controls for the section become available for the control of a following cut.

Other objects and further advantages of my invention will become apparent to those skilled in the art as the description proceeds.

In practicing my invention, which is adapted tobe employed at any of the retarder locations in a classification.

yard, I provide speed control means ,for each section of United States Patent O a retarder which measures the speed of a cut occupying the associated section and compares it with a preselected speed. Each retarder section is provided with a pressure control unit, and means are provided for controlling the pressure control unit from the s'peedcontrol unit to reduce the ditierence between the measured speed and the preselected speed. Means are also provided for controlling the pressure control unit for a'given retarder section from the speed control unit for the preceding section when both sections are occupied by the same cut, and for turning the control of a pressure control unit overto its own speed control unit when" the preceding section is vacated by the cut.

In accordance with one specific embodiment of my inno vention, which is adapted to be employed in conjunction with aclassification yard system of the type disclosed in the above-mentioned copending application, I provide one set of control apparatus for each group retarder in the yard. In a yard of the class described, each storage track is approached from a common hump track over a series of sections comprising an approach track section, a master. retarder including one or more detector track sections, one or more switch detector track sections following the master retarder, a group retarder approach track section, a group retarder including a plurality of track sections, and one or more switch detector track sections following the group retarder. Adjacent the entrance end of the master retarder, I provide means for weighing each car. Storage and transfer means, which may be in accordance with the above copending application, are employed for storing the weight information foreach cut and making it available to the group retarder location in the route of each cut when the cut occupies the detector track section in advance of the group retarder. A group retarder leaving speed computer, which may also be in accordance with that disclosed in the above copending application, is employed to select a desired leaving speed for each cut traversing the group retarder.

Each section of the group retarder is provided with a' pressure control unit, a radar velocity meter, a speed control unit, and a selected leaving speed storage unit, each of which may be in accordance with corresponding units disclosed in the above copending application. Each group retarder section is .also provided with a weight storage'unit. By circuits which will be described belowin detail, each section of the retarder is controlled in accordance with the leaving speed selected for the cut occupying the section. If the preceding section has been vacated, this control is exercised by the speed control unit for the occupied section. If the preceding section is still occupied by the cut, the control is exercised by the speed control unit for the preceding section. A group ofrelays are provided, which operate in a manner to be hereinafter more fully described, to mark the progressof each cut and to interconect the various control units described above to carry out the sequence oi control operations just re ferred to.

I shall first describe one embodiment of my invention in detail, and then shall point out the novel features thereof in claims.

I have illustrated an embodiment of my invention which is adapted to be employed for the control of a group retarder in a classification yard of the type disclosed in the above copending application. Only those components of the system disclosed in the above copending application which are necessary to the understanding of my invention have been illustrated, and in general these components have been illustrated in block diagram form. However, the correspondence between schematically illustrated components and those shown indetail in the above-mentioned copending application will be readily apparent to those skilled in the art as the description proceeds.

in order to simplify the illustration of the circuits employed in my invention, I have not shown the necessary power supplies indetail. One of these power supplies is a'conventional source of DC. voltage having positive and-negative terminals, connections to which are schematically indicated on the drawings by the reference In the drawings, FIGS. la through 1 when arranged side by side, comprise a schematic diagram of one embodiment of my invention.

Referring now to the drawings, I have illustrated a pair of routes in a classification yard. These routes terminate in two storage tracks T1 and T2, as shown in FIG. 1 These storage tracks are approached over a common route. As shown in FIG. la, the entrance of this common route comprises a hump followed by an approach track section AT. Following approach track section AT is a'master retarder comprising two track sections MRIT and MRZT. Following the master retarder are two switches, designated respectively 18W and 14W, which are provided with detector track sections 1-8T and 1-4T. These switches control the routes to storage tracks 1-8 and 1-4, respectively, as described in detail in the above copending application.

As pointed out in the above copending application, a number of track sections will normally be provided between each group retarder and the preceding switch. However, for the sake of simplicity I have shown only a single approach track section 1-2AT in this portion of the route. Approach track section 1-2AT is followed by a group retarder comprising two group retarder sections disposed in group retarder track sections 1-2GR1T and l-2GR2T.

The group retarder is followed at least by one switch 1-2W, having a detector track section 12T, which controls the routes to tracks T1 and T2.

Each of the track sections just described is, in practice, provided with track circuits in the manner fully disclosed in the above copending application. Since the majority of these track circuits are not involved in the operation of this embodiment of my invention, only the track relays in the track circuits associated with approach track section 1-2AT, group retarder track sections 1-2GR1T and l-ZGRZT, and switch detector track section 1-2T are shown. These track relays, respectively designated as Ti-ZATR (FIG. 1c), RlTR, RZTR (FIG. 1e), and 1-2TR (FIG. 1 are controlled by conventional D.C. track circuits including the rails of their respective track sections in a manner well-known in the art, such that they are energized when their respective sections are unoccupied and released when their respective sections are occupied. The circuits controlled by these track relays will be discussed in detail below.

Referring now to FIG. 1a, in accordance with this embodiment of my invention, a weigh-rail contactor WRC is located just inside the entrance end of master retarder track section MRIT as shown, to be actuated by the wheels of the cars entering section MRIT in accordance with the load on each wheel. In a manner explained more fully in the above-mentioned copending application, the response of contactor WRC is transmitted to weight coding storage, and transfer circuits 1, wherein means are provided to advance the weight information for each cut in step with the progress of the cut in its selected route, and finally, when the cut occupies detector track section l-ZAT, to energizing one or both of weight repeater relays 1-2ALP in accordance with the registered axle loading of the cut. In particular, for light cars weighing between 16 and 32 tons, a relay 1-2ALP is energized and relay 12AHP is released. For medium cars weighing between 32 and 50 tons, both of relays 1-2ALP and 12AHP are energized. For heavy cars weighing over 50 tons, relay 1-2AHP is energized and relay 1-2ALP is released. Since the circuits for performing this function do not form a part of my present invention, they are not shown in detail. However, they are fully described in the above-mentioned copending application, in which weigh-rail contactor WRC is shown in FIG. 18 and relays 1-2ALP and 1-2AHP are shown as ALP and AHP in FIG. 43.

Referring now to FIG. 1b, a V3 computer 2 is shown which corresponds to V3 computer 22 in FIG. 13 of the above-mentioned copending application. Insofar as my present invention is concerned, it is sufficient to note that this device supplies a DC voltage proportional to the desired group retarder leaving speed V3 for each cut between its output lead 3 and grounded lead 4 which is available while the cut occupies detector track section 1-2AT, which may correspond to track section CL4T as shown in FIG. 12 of the above-mentioned copending application. This voltage is supplied to input terminal a of storage unit l2GR1ESU, to be described, over lead 3 and front contact a of relay 1-2ATP.

Referring now to FIG. 1d, the first section of the group retarder is provided with a pressure control unit 1-2GR1 which is more fully described in the above-mentioned copending application. It is suflicient to note for the present application that this apparatus controls the braking force exerted by the first section of the group retarder in response to the actuation of the intake control magnets IHM, lHMM and lLM or exhaust magnets lXlM and 1X2M. As explained in the copending application, magnets IHM and lHMM control fast acting valves which in turn control the supply of fluid under pressure to actuating cylinders for the retarders. Magnet ILM controls a similar but smaller and faster valve, which also controls the admission of fluid under pressure to the actuating cylinders. Magnet IXlM controls a valve similar to that controlled by magnets lHM and IHMM, which controls the exhaust of fluid under pressure from the actuating cylinders. Magnet 1X2M controls a large capacity exhaust valve which is relatively slower to respond and which also controls the exhaust of fluid under pressure from the cylinders. In operation, exhaust magnet 1X2M may be energized alone, or in combination with magnet 1X1M, and one or more of intake magnets 1I-IM, IHMM, and 1LM are energized in combination in accordance with-the desired rate of response of the retarder as indicated by the weight of the cut. Magnet lLM alone is used in the control of light cuts, magnet IHMM alone is used in the control of medium weight cuts, and magnets lHM and lHMM are used for heavy cuts in order to get appropriate rates of response for these various weight classifications.

The pressure in the actuating cylinders of retarder control unit 1-2GR1 is indicated by the response of Bourdon tubes 5, 6, 7 and 8 connected by a conduit 9 to the supply manifold for the actuating cylinders, not shown. As more fully described in the above-mentioned copending application, Bourdon tube 5 is used to preset the second section of the group retarder. Its front contact a, in the embodiment here illustrated, is closed when the pressure in the first section exceeds 85 p.s.i., and its back contact b is closed when the pressure in the first section is less than 35 p.s.i. Bourdon tube 6 is adapted to close its front contact a when the pressure in the first section exceeds 82 p.s.i. and to close its back contact b when the pressure is less than p.s.i. This Bourdon tube is used to establish a ceiling for medium Weight cars, to preset the first section of the retarder for heavy cars, and to establish a standby pressure in the first section. Bourdon tube 7 closes its front contact a when the pressure exceeds 37 p.s.i. and its back contact b when the pressure goes below 30 p.s.i. This tube is used to establish a pressure ceiling for light cars and to preset the first section of the retarder for medium cars. Bourdon tube 8 closes its front contact a when the pressure exceeds 22 p.s.i. and closes its back contact I] when the pressure is below 15 p.s.i. This tube is used to preset the first section of the group retarder for light cars.

Referring now to FIG. 1 the second section of the group retarder is provided with a pressure control unit I-ZGRZ which may be identical with the first pressure control unit, just described. As fully described in the above copending application, this pressure control unit is provided with intake control magnets ZHM, ZHMM and 2LM, and with exhaust magnets 2X1M and ZXZM.

Exhaust magnet 2X2M is used alone, or in parallel with magnet ZXIM, for automatic control, magnet ZXEM controlling a fast acting valve of relatively small capacity, and magnet 2X2M controlling a slower acting valve of large capacity. For light cuts, magnet ZLM is used alone to control a high speed relatively low capacity intake valve. For medium weight cuts, intake magnet ZHMMis used alone to control a fast acting valve of the same size of that controlled by magnet ZXlM and of approximately twice the capacity of the valve controlled by magnet ZLM. Magnet ZHM controls a valve similar to that controlled by magnet ZHMM, and is used in parallel with magnet ZHMM to provide a rapid rate of response for the control of heavy cars.

Retarder control unit 1-2GR2 is provided with two Bourdon tubes and 11, which are connected to the fluid suply manifold in retarder control unit 1-2GR2 by a conduit 12. Bourdon tube 10 is set to close its front contact a at a pressure of 37 p.s.i., and to close its back contact b at a pressure of 30 p.s.i. This Bourdon tube is used to establish a pressure ceilling for light cars when back contact b of Bourdon tube 5 in the first section is closed. Bourdon tube 11 is set to close its front contact a when the pressure in the second section exceeds 70 p.s.i.-, and to close its back contact b when the pressure goes below 63 psi. It is used to preset the second section when the pressure in the first section is between 35 and 85 psi, and to establish a standby pressure in the second section.

A speed controllunit 13 (FIG. 1 is provided for the first section of the group retarder, and at times also controls the second section, as will be described. A second speed control unit 14 (FIG. 1e) is provided for the second section of the group retarder. These speed control units are identical with those described in the above copending application, and will, therefore, not be described in detail. Each of these speed control units includes a pair of control relays which are energized in accordance with the measured speed of the cut as compared with its desired speed.

In speed control unit 13, relay IASCR is energized and relay IBSCR is released when the speed of the cut is as desired. When the speed of the cut falls below the desired speed, relay EASCR is released and exhaust terminals f and g of the speed control unit are energized from terminal B of the battery over the back point of contact a and back contact b, respectively, of relay lASCR. If the speed of the cut is above the desired speed, both relays lASCR and lBSCR are energized, and intake terminal e of the speed control unit is energized from terminal B of the battery over the front point of contact a of relay lASCR and front contact a of relay EBSCR.

Speed control unit 14 in MG. lle operates in the same 7 manner as described for speed control unit 13 in FIG. 1c. That is, relay ZBSCR corresponds to reiaylBSCR in unit 13 and relay ZASCR corresponds to relay lASCR in unit 13. Accordingly, when the speed of the cut is correct, none of the terminals c, and g of unit 14- are energized. If the speed of the cut is too high, intake terminal e is energized over front contacts a of relays ZBSCR and ZASCR. If the speed of the cut is too low, exhaust terminals .1 and g are energized over back contacts a and b, respectively, of relay ZASCR.

Speed control units 13 and 14 further include input terminals a and b, to which the selected speed and measured speed, respectively, for each out are supplied in terms of voltages proportional to their values, as will appear.

input terminal a of speed control unit 13 (FIG. 1c) has an energizing circuit extending from output terminal 0 of storage unit 1-2GRl-ESU, to be described, over 'ront contact 0 of relay RlTP. Input terminal bof speed control unit 13 has an energizing circuit extending from output terminal a of radar velocity meter 1'5, to be described, over front contactb of relay RlTP. 'Accordingl-y, terminals 0 and b are energized with voltages propor-- tional to the desired speed and the measured speed, respectively, of cuts occupying track section lZGRlT.

input terminal a of speed control unit '14 (FIG. 1e) has-an energizing circuit extending from output terminal -c of storage unit -12G-R2ESU, to be described, over front contact 1 of relay RZTP. Input terminal b of speed control unit 34 has an energizing circuit extending from output terminal a of radar velocity meter 16, to be described, over front contac't'e of relayRZTP. Accordin iy, terminals :2 and b are energized with voltages proportional to the desired speed and the measured speed, respectively, of cuts occupying track section 14 6112? Each section of the group retarder is provided with a radar velocity meter, radar velocity meter 1'5 being provided for the first section of the group retarder (FIG. 10) and radar velocity meter 16 being provided for the second section (FIG. 12'). Terminals b of these radar velocity meters are connected to suitable antennas 17 and 19, respectively, through conventional wave guides 18 and 20, respectively, as schematically illustrated, and the output terminals a of these meters are at times connected to the input terminals b of their corresponding speed control units, as has been described.

As shown in FIG. le, antenna 17 for radar velocity meter 15 is located adjacent the exit end of track section l-ZGR'lT in 'the first section of the group retarder and is connected to input terminal b of velocity meter 15 over wave guide 18. Antenna 19 for radar velocity meter 16 is located adjacent the exit end of track section 1-2GR1T and is connected to input terminal b of meter 16 over Wave guide 2%. Velocity meters 16 and 16 accordingly respond to measure the speeds of cuts occupying their respective sections.

The leaving speed for each cut from the group retarder is established by V3 computer 2, described above. The leaving speed computed by computer 2 is made available to speed control unit 13 in the first section of the group retarder from a first electronic storage unit l-ZGR1ESU (FIG. 10). The computed leaving speed is made available to the second section of the groupretarder from a second electronic storage unit l2GR2ESU (FIG. 1e).

These storage units have been described in detail in the above cop'ending application and will accordingly not be described here. It is sufficient for the purposes of describing my invention to note that, when required by the group retarder, these storage units provide output voltages between their output terminals 0 and ground terminals d which are a measure of the stored computed leaving speed. These output voltages are at times con- 'nected to terminals a of speed control units 13 and 14 of the group retarder by the circuits described above. A Voltage to be stored in one of these units is supplied between input terminal a of the unit and ground, and the storage is made final and maintained when a storage relay RlI-l in unit l-ZGRl-ESU and RZH in unit l-ZZGRZ-ESU is energized by a voltage applied from terminal B of the battery to input terminal b of the storage unit.

Terminal a of storage unit 12GR1-ESU is energized from output lead 3 of V3 computer 2 over front contact a of relay i-ZATP as previously described. Terminal b of storage unit l2GRl-ESU has an energizing circuit which extends from terminal B of the battery over front contact d of relay RlTP. Accordingly, relay RlH is picked up and the storage in this unit is made final when track section 12GR1T is occupied.

Terminal at of storage unit l-ZGRZ-ESU is energized from output terminal c of storage unit 1-2GRi-ESU over lead 96 and back contact I: of relay RZTP. The stored desired speed Voltage in unit 12GR1ESU is accordingly supplied to unit 1-2GR2ESU prior to the occupancy of track section 12GR 2T. Terminal b of storage unit 1-2GR2-ESU is energized from terminal B of the battery over front contact g of relay RZTP to make 7 the stored voltage final when track section 1-2GR2T is occupied.

The first section of the group ret-arder has a lever RIMC (FIG. 1d), and the second section has a corresponding lever RZMC (FIG. 1 Each of these levers has a series of control contacts, comprising a first set of contacts A which are closed in the automatic condition of the apparatus, a second set of contacts H, closed when it is desired to control a heavy or a medium cut manually, a third set of contacts L, closed when it is desired to control a light out manually, and a fourth set of contacts 0, closed when it is desired to open the retarder.

A group of control relays are provided for marking the progress of cuts through the group retarder, and for controlling the sequence of operation of the group retarder during its occupancy by a cut. As shown in FIG. 10, these relays comprise track repeater relays 1-2ATP, RITP and RITPP, end-of-cut relays GAEC and RIEC, and relay 1-2RC, which is picked up when the cut occupies both sections 1-2GR1T and 1-2GR2T. In FIG. 1e, there are shown track repeater relay RZTP and end-ofcut relay RZEC. The control circuits for these relays will now be described.

Track repeater relay 1-2ATP (FIG. 10) is energized over an obvious circuit which extends from terminal B of the battery over back contact a of track relay LZATR, and through the winding of the relay to terminal N of the battery. This relay is accordingly energized when approach track section 1-2AT is occupied.

Repeater relay RlTP (FIG. 10) has an obvious energizing circuit which extends from terminal B of the battery over back contact a of relay RlTR and through the Winding of the relay to terminal N of the battery. This relay is accordingly picked up when track section 1- 2GR1T is occupied.

Repeater relay RITPP (FIG. 1c) has a pickup circuit which extends from terminal B of the battery over the front point of contact a of relay RITP and through the winding of the relay to terminal N of the battery. Relay RlTPP has a stick circuit which extends from terminal B of the battery over back contact b of relay RlEC, to be described, its own front contact a, and through the winding of the relay to terminal N of the battery. This relay is accordingly picked up when track section 1 2GR1T is occupied, and, as will appear, it is then held up until track section 1-2GR1T is cleared.

Repeater relay RZTP (FIG. 10) has an obvious energizing circuit which extends from terminal B of the battery over back contact a of track relay RZTR and through the winding of the relay to terminal N of the battery. This relay is accordingly picked up when track section 1-2GR2T is occupied.

End-of-cut relay GAEC (FIG. 10) has a pickup circuit which extends from terminal B of the battery over back contact d of relay 1-2ATP, front contact 1'' of relay RITP, and through the winding of the relay, and over back contact of relay RIEC to terminal N of the battery. Relay GAEC has a stick circuit which extends from terrninal B of the battery over its own front contact a, through its winding, and over back contact 0 of relay RIEC to terminal N of the battery. This relay is accordingly picked up with track section 1-2GR1T occupied when track section 1-2AT has been vacated, and once picked up, is held up until track section l-ZGRIT is cleared. #Relay GAEC is made somewhat slow to release, as indicated, for reasons to appear.

End of cut relay RIEC (FIG. 1c) has a pickup circuit which extends from terminal B of the battery over the back point of contact a of relay RITP, lead 21, front contact a of relay RZTP (FIG. 1e), lead 22, front contact b of relay GAEC, through the winding of relay RIEC, lead 23, and over the back point of contact a of relay RZEC (FIG. Is) to terminal N of the battery. Relay RTIEC has a stick circuit which extends from terminal B of the battery over its own front contact a, through its winding, over lead 23, and over the back point of contact a of relay RZEC to terminal N of the battery. This relay is accordingly picked up when track section 1-2GR1T is cleared and is held up until track section 1-2GR2T is cleared. Relay RIEC may be made somewhat slow to release, as indicated, for reasons which will appear.

Relay 12RC (FIG. 10) has a pickup circuit which ex tends from terminal B of the battery over front contact b of relay RZTP (FIG. 1e), lead 24, through the winding of relay 1-2RC, and over back contact d of relay RIEC to terminal N of the battery. Relay 12RC has a stick circuit which extends from terminal B of the battery over its own front contact a, through the winding of the relay, and over back contact d of relay RIEC to terminal N of the battery. This relay is accordingly picked up when track section 1-2GR2T is occupied, as indicated by the energized condition of relay RZTP, and while the cut is still shunting section 1-2GR1T, as indicated by the released condition of end-of-cut relay RIEC.

Relay RZEC (FIG. 1e) has a pickup circuit which extends from terminal B of the battery over back contact a of track relay 1-2TR (FIG. 1 lead 25, through the winding of relay RZEC, lead 26, over front contact e of relay RIEC (FIG. 10), lead 27, and over back contact 0 of relay RZTP to terminal N of the battery. Relay R2EC has a stick circuit which extends from terminal B of the battery over back contact a of relay 1-2TR, lead 25, through the winding of relay RZEC, and over the front point of contact a of relay RZEC to terminal N of the battery. Relay RZEC is accordingly picked up when track section 1-2GR2T is cleared, and is held up as long as track section 1-2T is occupied.

The first section of the group retarder is provided with two weight storage relays RLI and RH1 (FIG. 10) and the second section is provided with two weight storage relays RL2 and RHZ (FIG. 16). The control circuits for these storage relays will now be described.

Relay RLl (FIG. 10) has a pickup circuit which extends from terminal B of the battery over front contact a of relay 12ALP (FIG. 1a), lead 28, front contact 0 of relay 1-2ATP, back contact c of relay GAEC, and through the winding of relay RLI to terminal N of the battery. Relay RL1 has a stick circuit which extends from terminal B of the battery over front contact e of relay RITP, its own front contact a, and through the winding of the relay to terminal N of the battery. This relay is accordingly picked up if relay 1-2ALP is picked up when a cut occupies approach track section 1-2AT, and is held up thereafter as long as track section 1-2GR1T is occupied.

Relay RHI (FIG. 10) has a pickup circuit which extends from terminal B of the battery over front contact a of relay l-ZAHP (FIG. la), lead 29, front contact b of relay I-ZATP, back contact d of relay GAEC, and through the winding of relay RH1 to terminal N of the battery. Relay RI-Il has a stick circuit which extends from terminal B of the battery over front contact e of relay RlTP, its own front contact a, and through its winding to terminal N of the battery. This relay is accordingly picked up if relay 1-2AHP is picked up when track section 1-2AT is occupied, and is held up thereafter as long as track section 1-2GRIT is occupied.

Relay RL2 (FIG. 1e) has a pickup circuit which extends from terminal B of the battery over front contact I] of relay 1-2RC, front contact c of relay RLI, lead 30, and through the winding of relay RL2 to terminal N of the battery. Relay RL2 has a stick circuit which extends from terminal B of the battery over front contact d of relay RZTP, its own front contact a, and through the winding of the relay to terminal N of the battery. Relay RL2 is accordingly picked up if relay RLI is picked up when relay 1-2RC is energized, and once picked up, is held up as long as section l-ZGRZT is occupied.

Relay RHZ (FIG. 12) has a pickup circuit which extends from terminal B of the battery over front contact of relay 1-2RC (FIG. front contact 0 of relay RHI, lead 31, and through the winding of relay RHZ to terminal N of the battery. Relay RH-Z has a stick circuit which extends from terminal B of the battery over front contact a! of relay RZTP, its own front contact a, and through the winding of the relay to terminal N of the battery. Relay RHZ is accordingly picked up if relay RHl is picked up when relay 1'2RC is picked up, and once picked up, is held up as long as track section 1- 2GR2T is occupied.

Relay AP (FIG. 111) is picked up when the retarder is under automatic control. This relay has an energizing circuit which extends from terminal B of the battery over the contacts of lever RZMC (FIG. If) in its A position, lead 32, the contacts of lever RlMC in its A position, and through the winding of relay AP to terminal N of the battery.

Two additional control relays are associated with the first section of the group retarder. These are relays lHPR and NPR, shown in FIG. 1d, the control circuits for which will now be described.

Relay lHPR (FIG. 1d.) has an obvious pickup circuit extending from terminal B of the battery over the contacts of lever RlMC in its H position and through the winding of the relay to terminal N of the battery. The lever is moved to its H position to energize this relay whenever it is desired to apply manually a heavy braking pressure suitable for cuts of heavy or medium weight.

Relay 10PR (FIG. 1d) has a first pickup circuit extending from terminal B of the battery over the contacts of lever RlMC in its 0 position and through the winding of the relay to terminal N of the battery. The lever is moved to position 0 when it is desired to open the retarder, and relay ltlPR will be continuously energized while the lever is in this position. Relay NPR has a second pickup circuit which extends from terminal B of the battery over back contact -c of relay RiTPP (FIG. 10), lead 33, front contact e of relay AP (FIG. 1d), lead 34, the back point of contact 1 of relay RHl, the front point of contact 1 of relay RLI, lead 35, front contact a of Bourdon tube 8, closed when the pressure in the first section exceeds 22 p.s.i., lead 3%, back contact 0 of relay lHPR, and through the winding of relay ltlPR to terminal N of the battery. This circuit is employed to pick up relay 10PR before section ll ZGRliT is occupied, but after it has been established that the weight of the next cut is light, to maintain the preset pressure of the first section below '22 p.s.i. Relay ltlPR has a third pickup circuit which extends from terminal B of the battery over the contacts of lever RlMC in its L position, lead 37, front contact a of Bourdon tube 7, closed when the pressure in the first section exceeds 37 p.s.i., lead 3'6, back contact 0 of relay II-IPR, and through the winding of relay lliPR to terminal N of the battery. This circuit is used to establish a pressure ceiling of 37 p.s.i. for light cuts under manual control. Relay NPR has a fourth pickup circuit extending from terminal e of speed control unit 13 (FIG. 1c), energized when the speed of the cut is above the desired value to request more air pressure in the retarder, lead 38, lead 39, front contact b of relay R-lTPP, lead 41, front contact 0 of relay AP, lead 42, the back'point of contact e of relay RHl, front contact h of relay RLI, lead 43, lead 37, front contact a of Bourdon tube 7, lead '36, back contact 0 of relay lHPR, and through the winding of relay ltlPR to terminal N of the battery. This circuit is employed to enforce a pressure ceiling of 37 p.s.i. on light cars under automatic control. Relay ltlPR has a fifth pickup circuit extending from terminal B of the battery over back contact 0 of relay RlTPP, lead 33, front contact e of relay AP, lead 34, the front point of contact 7 of relay RHI, the front point of contact g of relay RLl, lead 43, lead 37, front contact a of Bourdon tube 7, lead 36,

10 back contact 0 of relay IHPR, and through the winding of relay liiPR to terminal N of the battery. This circuit is used in presetting the first section of the retarder for medium weight cars to prevent the pressure from exceeding 37 p.s.i. Relay NPR has a sixth pickup circuit extending from terminal e of speed control unit 13 (FIG. 10), over leads 38 and 39, front contact b of relay RlTPP, lead 41, front contact 0 of relay AP, lead 42, the front point of contact e of relay RHl, the front point of contact e of relay RLl, lead 44, front contact a of Bourdon tube 6, closed when the pressure in the first section exceeds 82 p.s.i., lead 36, back contact 0 of relay IHPR, and through the winding of relay NPR to terminal N of the battery. This circuit is used to establish a maximum pressure of 82 p.s.i. for medium weight cuts under automatic control. Relay ltPPR has a seventh pickup circuit extending from terminal B of the battery over back contact c of relay RITPP, lead 33, front contact e of relay AP, lead 34, the back point of contact of relay RHl, the back point of contact 1 of relay RLl, lead 44, front contact a of Bourdon tube 6, lead 36, back contact 0 of relay 1HPR, and through the winding of relay ltlPR to terminal N of the battery. This circuit is used to establish a standby pressure in the group retarder at a maximum of 82 p.s.i. Relay ltlPR has an eighth pickup circuit extending from terminal B of the battery over back contact 0 of relay RITPP, lead 33, front contact e of relay AP, lead 34, the front point of contact ;f of relay RHl, the back point of contact g of relay RLl, lead 44, front contact a of Bourdon tube 6, lead 36, back contact 0 of relay lHPR, and through the winding of relay NPR to terminal N of the battery. This circuit is used in presetting the first section for heavy cars to prevent the pressure from exceeding 82 p.s.i.

Three additional control relays are provided for the second section of the retarder. These are relays lVPR, ZHPR, and "NPR, as shown in FIG. 3. The control circuits for these relays will now be described.

Relay IVPR is of the type having two windings, either of which when energized is suflicient to open the back contacts and close the front contacts of the relay. Since this relay may be of conventional construction, it will not be further described in detail. It has a first pickup circuit extending from terminal B of the battery over front contact d of relay AP (FIG. 1d), lead 45, back contact d of relay RHZ, back contact d of relay RLZ, lead 45, front contact a of Bourdon tube 5, closed when the pressure in the first section exceeds 85 p.s.i., lead 48, and through the upper winding of relay lVPR to terminal N of the battery. As will appear, this circuit is employed to preset the second section when the pressure in the first section is above 85 p.s.i. Relay lVPR has a second pickup circuit which extends from terminal B of the battery over front contact d of relay AP, lead 45, back contacts d of relays RHZ and RL2 in series, lead 46, back contact b of Bourdon tube 5, closed when the pressure in the first section is below 35 p.s.i., lead 49, and through the lower winding of relay lVPR to terminal N of the battery. As will later appear, the pressure in the second section is maintained between 30 and 37 p.s.i. by circuits controlled by relay IVPR when the pressure in the first section is below 35 p.s.i.

Relay ZHPR (FIG. 1 has an obvious pickup circuit extending from terminal B of the battery over the contacts of lever RZMC in its H position and through the winding of the relay to terminal N of the battery. Accordingly, relay ZI-IPR is energized when the lever is set manually to its H position, and, as will appear, it then controls circuits which energize intake magnets ZHM and ZHMM in' parallel to provide a rapid increase in pressure, and to maintain a relatively high pressure, in the second section during the manual control of heavy or medium weight cuts.

Relay ZGPR (FIG. 1]) has a first pickup circuit extending from terminal B of the battery over the contacts of lever RZMC in its position and through the winding of the relay to terminal N of the battery. This relay is thus energized when it is desired to open the second section of the retarder, and, as will appear, completes circuits to maintain exhaust magnet 2X2M energized at such times. Relay ZOPR has a second pickup circuit extending from terminal B of the battery over front contact d of relay AP (FIG. la), lead 45, back contacts d of relays RHZ and RL2 in series, lead 47, back contact o of relay IVPR, lead 82, front contact a of Bourdon tube 11, closed when the pressure in the second section is above 70 p.s.i., lead 50, back contact 0 of relay ZHPR, and through the winding of relay ZOPR to terminal N of the battery. This circuit is used to establish a standby pressure in the second section below 70 p.s.i. Relay 20PR has a third pickup circuit which extends from terminal B of the battery over the contacts of lever R2MC in its L position, lead 51, lead 52, front contact a of Bourdon tube 10, closed when the pressure in the second section exceeds 37 p.s.i., lead 50, back contact 0 of relay ZI-IPR, and through the winding of relay 20PR to terminal N of the battery. This circuit is used during the manual control of light cuts to maintain the pressure in the second section below 37 p.s.i. Relay 20PR has a fourth pickup circuit extending from terminal e of the first section speed control unit 13 (FIG. over leads 38 and 40, the front point of contact d of relay 1-2RC, lead 55, front contact 11 of relay AP, lead 56, the back point of contact 0 of relay RHZ, front contact b of relay RL2, lead 54, lead 51, lead 52, front contact a of Bourdon tube 10, lead 50, back contact c of relay ZHPR, and through the winding of relay PR, to terminal N of the battery. This circuit is employed during the time that the cut occupies both sections of the group retarder to maintain a ceiling of 37 p.s.i. for light cuts, even though increased braking may then be requested by the first action speed control unit. Relay 20PR has a fifth pickup circuit which extends from terminal B of the battery over front contact d of relay AP (FIG. 1d), lead 45, back contact d of relay RHZ, back contact a. of relay RL2, lead 46, back contact b of Bourdon tube 5 in the first section, lead 49, front contact b of relay IVPR, which will be energized if the circuit is energized to this point, leads 53 and 52, front contact a of Bourdon tube 10, lead 50, back contact 0 of relay ZHPR, and through the winding of relay 20PR to terminal N of the battery. This circuit is employed to maintain the preset pressure below 37 p.s.i. when the pressure in the first section is below p.s.i.

The energizing circuits for the control relays having been described, the circuits controlled thereby for actuatting the intake and exhaust magnets in the pressure control units for the first and second sections of the retarder will now be described.

Intake magnet lI-IM (FIG. 1d) has a first pickup circuit extending from terminal B of the battery over the front point of contact a of relay IHPR, lead 56, and through the winding of magnet IHM to terminal N of the battery. This circuit is used in the manual control of heavy and medium cuts to assist in maintaining a high braking pressure. Magnet lHM has a second pickup circuit which extends from terminal e of speed control unit 13 (FIG. 1c), leads 38 and 39, front contact b of relay RITP, lead 41, front contact c of relay AP, lead 42, front contact d of relay RHl, back contact at of relay RLI, lead 57, the back point of contact a of relay IHPR, lead 56, and through the winding of magnet IHM to terminal N of the battery. This circuit is used to energize magnet IHM in the control of heavy cuts when the combined speed characteristics of the cut demand more braking as evidenced by the energized condition of terminal e of speed control unit 13.

Magnet ll-IMM has a first pickup circuit extending from terminal B of the battery over the front point of contact b of relay lI-lPR, lead 58, lead 60, and through the winding of magnet lI-IMM to terminal N of the battery. By this circuit, magnet lI-IMM is energized in conjunction with magnet IHM to bring about a rapid increase in braking pressure for the manual control of heavy and medium cuts. Magnet lHMM has a second pickup circuit extending from terminal e of speed control unit 13 over leads 38 and 39, front contact b of relay RlTPP, lead 41, front contact 0 of relay AP, lead 42, the front point of contact 2 of relay RI-Il, the back point of contact e of relay RLl, lead 61, the back point of contact b of relay IHPR, leads 53 and 60, and through the winding of relay lHMM to terminal N of the battery. This circuit is employed to energize magnet IHMM together with magnet IHM in the automatic control of heavy cuts. Magnet IHMM has a third pickup circuit which extends from terminal 2 of speed control unit 13 over leads 38 and 39, front contact b of relay RITPP, lead 41, front contact c of relay AP, lead 42, the front point of contact e of relay RHI, the front point of contact e of relay RLl, lead 44, back contact b of Bourdon tube 5, closed when the pressure in the first section is below 73 p.s.i., leads 59 and 60, and through the winding of magnet IHMM to terminal N of the battery. This circuit is used in the automatic control of medium weight cuts to apply increased braking pressure when requested by the energized condition of speed control terminal e if the pressure in the first section is below 75 p.s.i. Magnet ll-IMM has a fotuth pickup circuit which extends from terminal B of the battery over back contact 0 of relay RITPP (FIG. 1c), lead 33, front contact e of relay AP, lead 34, the back point of contact f of relay RI-Il, the back point of contact 1 of relay RLI, lead 44, back contact b of Bourdon tube 6, leads 59 and 60, and through the winding of magnet lHMM to terminal N of the battery. This circuit is used to establish a standby pressure of at least 75 p.s.i. in the first section. Magnet lHMM has a fifth pickup circuit extending from terminal B of the battery over back contact c of relay RITPP, lead 33, front contact e of relay AP, lead 34, the front point of contact 1 of relay RHI, the back point of contact g of relay RLl, lead 44, back contact b of Bourdon tube 6, leads 59 and 60, and through the winding of magnet lHMM to terminal N of the battery. This circuit is used to preset the first section of the retarder to at least 75 p.s.i. when the approach of a heavy cut is indicated.

Magnet 1LM (FIG. 1d) has a first pickup circuit extending from terminal B of the battery over back contact c of relay RlTPP (FIG. 10), lead 33, front contact e of relay AP, lead 34, the back point of contact 1 of relay RHl, the front point of contact 1 of relay RLI, lead 35, back contact b of Bourdon tube 8, closed when the pressure is below 15 p.s.i., lead 62, and through the winding of magnet 1LM to terminal N of the battery. This circuit is used to preset the first section to at least 15 p.s.i. on the approach of a light weight cut. Magnet ILM has a second pickup circuit extending from terminal B of the battery over the contacts of lever RIMC (FIG. 1d) in its L position, lead 37, back contact b of Bourdon tube 7, lead 62, and through the winding of magnet lLM to terminal N of the battery. This circuit is used to maintain the pressure in the first section above 30 p.s.i. in the manual control of light cuts. Magnet 1LM has a third pickup circuit extending from terminal B of the battery over back contact 0 of relay RlTPP (FIG. 10), lead 33, front contact e of relay AP, lead 34, the front point of contact 1 of relay RHl, the front point of contact g of relay RLl, leads 43 and 37, back contact b of Bourdon tube 7, closed when the pressure in the first section is below 30 p.s.i., lead 62, and through the winding of magnet lLM to terminal N of the battery. This circuit is used to preset the first section to at least 30 p.s.i. for me dium weight cuts. Magnet lLM has a fourth pickup circuit extending fromterrninal e of speed control unit 13 over leads 38 and 39, front contact b of relay RlTPP, lead 41, front contact of relay AP, lead 42, the back point of contact e of relay RHl, front contact h of relay RH leads 43 and 37, back contact b of Bourdon tube '7, lead 62, and through the winding of magnet lLM to terminal N'of the battery. This circuit is used in the automatic control of light cuts to maintain the pressure above 30 psi. when the speed control unit requests more braking.

Exhaust magnet lXlM (FIG. 1d) has an energizing circuit extending from terminal 1 of speed control unit 13 (FIG. 1c), which is energized when it is desired to reduce the braking force during automatic control, over leads 63 and 64, front contact a of relay AP, lead 66, front contact b of relay RHI and front contact b of relay RH in multiple, thus providing a circuit path for any weight registration other than 0, lead 67, back contact a of relay ltiPR, lead 68; and through the winding of magnet lXlM to terminal N of the battery. Magnet lXlM is accordingly energized during automatic control when the combined speed characteristics of the out are less than the desired value.

Exhaust magnet IXZM (FIG. 1d) has a first energizing circuit extending from terminal B of the battery over the front point of contact b of relay IOPR, lead 6%, and through the winding of magnet 1X2M to terminal N of the battery. Magnet 1X2M is accordingly energized under any of the conditions previously described in which relay NPR is energized. Exhaust magnet IXZM has a second energizing circuit extending from terminal g of speed control unit 13, which is energized when the combined speed characteristics of a out under automatic con trol are below the desired value, over leads 70 and 72, front contact b of relay AP, lead 73, front contacts 2' of relay RL1 and g of relay RHI in multiple, lead 74, the back point of contact b of relay IGPR, lead 69, and through the Winding of magnet IXZM to terminal N of the battery. Magnet lXZM is accordingly energized in parallel with magnet lXlM during automatic speed control when it is desired to reduce the braking pressure. As previously described, under these conditions, magnet lXlM provides a rapid response, which is quickly sensed by the velocity meter, and magnet 1X2M provides additional capacity when its associated valve is opened.

Turning now to the control magnets of second section pressure control unit 1-2GR2, intake magnet ZHM (FIG. 1 has a first energizing circuit extending from terminal B of the battery over the front point of contact a of relay ZHPR, leads 75 and 76, and through the winding of magnet ZHM to terminal N of the battery. This circuit is employed to assist in establishing and maintaining a high pressure during the manual control of heavy and medium cuts. Magnet ZHM has a second energizing circuit which extends from terminal 0 of the first section speed control unit 13 (FIG. 10) over leads 38 and 40, the front point of contact d of relay l-ZRC, lead 55- front contact h of relay AP, lead 5 6, front contact b of relay REE, back contact c of relay RLZ, lead '77, the back point of contact a of relay ZHPR, leads 75 and '75, and through the winding of magnet ZHM to terminal N of the battery. This circuit is used during automatic control of heavy cars when additional braking isrequested by the first section speed control unit during the control of the second section by the first section speed control unit when both sections are occupied by a cut. Magnet Zl-IM has a third energizing circuit extending from terminal B of the battery over front contact d of relay AP (FIG. 1d), lead 45, back contacts d of relays RHZ and RLZ in series, lead 46, front contact a of Bourdon tube 5 (FIG. 1d) lead 48, front contact'a of relay IVP'R, lead 76, and through the winding of magnet ZHM to terminal N of the battery. This circuit is employed to maintain the standby pressure in the second section at the highest possible value (for example, 110 psi.) if the pressure in the first section exceeds 85 psi Magnet ZHM has a fourth energizing circuit extending from terminal e of speed control unit 14 (FIG. 1e) over lead 78, the back point of contact d of relay l-ZRC, lead 55, front contact h of relay AP, lead 56, front contact b of relay RHZ, back contact 0 of relay RLZ, lead '77, the back point of contact a of relay ZHPR, leads and 76, and through the winding of magnet ZHM to terminal N of the battery. This circuit is used when a out has cleared the first section of the group retarder to assist in rapidly increasing the braking pressure for heavy cuts when requested by the energized condition of terminal e of speed control unit 14.

Magnet ZHMM (FIG. 1f) has a first energizing circuit which extends from terminal B of the battery over the front point of contact b of relay ZHPR, leads 79 and 8b, and through the winding of magnet ZHMM to terminal N of the battery. Magnet ZHMM is accordingly energized in parallel with magnet ZHM during the manual control of heavy and medium cuts. Magnet ZHMM has a second energizing circuit which extends from terminal e of the first section speed control unit 31 over leads 33 and 40, the front point of contact d of relay 1-2RC, lead 55, front contact h of relay AP, lead 56, the front point of contact 0 of relay RHZ, lead 81, the back point of contact b of relay ZHPR, leads 79 and 8t), and through the winding of magnet Z-HMM to terminal N of the battery. Magnet ZHMM is accordingly energized during the control of the second section by the first section speed control, when terminal e of speed control unit 13 is energized and tie cut is of either medium or heavy weight. Magnet ZHMM has a third energizing circuit extending from terminal B of the battery over front contact at of relay AP, lead 45, back contacts d of relays RHZ and RL1; in series, lead 47, back contact 6 of relay IVPR, lead 82, back contact b of Bourdon tube 11, closed when the pressure is below 63 p.s.i., leads 83 and 80, and through the winding of magnet ZHMM to terminal N of the battery. This circuit keeps the pressure in the second section above 63 psi. under standby conditions. Magnet ZHMM has a fourth energizing circuit which extends from terminal e of speed control unit 14 (FIG. 1e), over lead '73, the back point of contact d of relay 1-2RC, lead 55, front contact h of relay AP, lead 56, the front point of contact c of relay RHZ, lead 81, the back point of contact b of relay ZHPR, leads 79 and 8t), and through the Winding of magnet ZHMM to terminal N of the battery. This circuit is employed in the automatic control of either heavy or medium cuts, after the first section has been cleared, when additional braking pressure is requested by the second section speed control unit 14.

Magnet ZLM (FIG. 1 has a first energizing circuit which extends from terminal B of the battery over the contacts of lever RZMC in its L position, leads 51 and 52, back contact b of Bourdon tube 1%, closed when the pressure in the second section is below 30 psi, lead 34, and through the winding of magnet ZLM to terminal N of the battery. This circuit keeps the pressure in the second section above 39 psi. during the manual control of light cuts. Magnet ZLM has a second energizing circuit which extends from terminal 2 of speed control unit 13 over leads 33 and as, the front point of contact (I of relay 12RC, lead 55, front contact h of relay AP, lead 56, the back point of contact 0 of relay RHZ, front contact b of relay RLZ, lead 54, lead 51, lead 52, back contact I) of Bourdon tube 10, lead 34, and through the winding of magnet ZLM to terminal N of the battery. This circuit is employed in the automatic control of light cuts while such cuts span both sections, when the first section speed control requests more braking and the pressure in the second section is below 30 psi. Magnet ZLM has a third energizing circuit which extends from terminal 2 of speed control unit 14 (FIG. 1e) over lead 78, the back point of contact d of relay 1-2RC, lead 55, front contact it of relay AP, lead 56, the back point of contact 0 of relay RHZ, front contact b of relay RLZ,

leads 54, 51 and 52', back contact b of Bourdon tube 10, lead 84, and through the winding of magnet ZLM to terminal N of the battery. This circuit is used in the control of the second section from the second section speed control unit after a cut has cleared the first section to maintain the pressure above p.s.i. for light cuts when increased pressure is requested by the speed control unit. Magnet ZLM has a fourth energizing circuit which extends frorn terminal B of the battery over front contact d of relay AP (FIG. 1d), lead 45, back contacts d of relays RH2 and RL2 in series, lead 46, back contact b of Bourdon tube 5, closed when the pressure in the first section is below p.s.i., lead 49, front contact b of relay IVPR, leads 53 and 52, back contact b of Bourdon tube 10, closed when the pressure in the second section is below 30 p.s.i., lead 84, and through the winding of magnet 2LM to terminal N of the battery. This circuit is used to preset the second section and maintain its pressure above 30 p.s.i. when the pressure in the first section is below 35 p.s.i.

Exhaust magnet ZXIM has a first energizing circuit which extends from terminal of first section speed control unit 13 over leads 63 and 65, the front point of contact f of relay 1-2RC, lead 35, front contact 1 of relay AP, lead 86, front contacts 1 of relays RLZ and RHZ in multiple, lead 87, back contact b of relay ZttPR, lead 88, and through the winding of magnet ZXlM to terminal N of the battery. Magnet 2X1M is energized by this circuit to cause a relatively rapid decrease in pres sure in the automatic control of cuts of light, medium or heavy weight when both sections of the retarder are occupied and reduced pressure is requested by the first section speed control unit 13. Magnet 2X1M has a second energizing circuit which extends from terminal 1 of the second section speed control unit 14 (FIG. 1e) over lead 89, the back point of contact 1 of relay l-ZRC, lead 85, front contact 1 of relay AP, lead 86, front contacts 1 of relays RLZ and RHZ in multiple, lead 87, back contact b of relay ZtlPR, lead 88, and through the winding of magnet 2X1M to terminal N of the battery. This circuit functions the same as the previously traced circuit, except that it is operative after a cut has cleared the first section of the group retarder and is being controlled by the second section speed control unit 14.

Exhaust magnet 2X2M has a first energizing circuit extending from terminal B of the battery over the front point of contact a of relay ZGPR, lead $0, and through the Winding of magnet 2X2M to terminal N of the battery. This circuit is employed to exhaust the retarder cylinders under the various conditions described above in which relay 20PR is energized. Magnet 2X2M has a second energizing circuit which extends from terminal g of speed control unit 13 over leads 7t] and 71, the front point of contact e of relay I-ZRC, lead 91, front contact g of relay AP, lead 92, front contacts e of relays RLZ and RH2 in multiple, lead 93, the back point of contact a of relay ZtiPR, lead 90, and through the winding of magnet ZXZM to terminal N of the battery. This circuit is employed to obtain reduced pressure in the automatic operation of the second section by the first section speed control. Magnet 2X2M has a third energizing circuit extending from terminal g of speed control unit 14 over lead 94, the back point of contact c of relay 12RC, lead 91, front contact g of relay AP, lead 92, front contact e of relays RLZ and RHZ in multiple, lead 93, the back point of contact a of relay ZOPR, lead 96, and through the winding of magnet 2X2M to terminal N of the battery. This circuit is employed to obtain reduced pressure in the automatic operation of the second section by the first section speed control. This circuit is used during the automatic control of the second section from the second section speed control unit 14 after a cut has cleared the first section.

The structure and arrangement of this embodiment of my invention having been described, its operation under various typical conditions will now be described.

The manual operation of the first section of the group retarder will first be considered. For the manual control of heavy cuts, lever RlMC is moved to the H position, causing relay 1HPR to pick up and magnets lHM and IHMM to be energized in parallel by their previously traced circuits over the front points of contacts a and b, respectively, of relay IHPR. The lever is left in the H position until the desired amount of braking has been obtained. For light cuts, the operation is semi-automatic. The lever is moved to its L position, energizing the movable contact member of Bourdon tube 7 over lead 37. When the pressure rises above 37 p.s.i., front contact a of this Bourdon tube will close, and relay 10PR will be picked up over its previously traced circuit including lead 36 and back contact c of relay IHPR. Exhaust magnet IXZM will then be ener' ized over its previously traced circuit including the front point of contact b of relay NPR, and the pressure will be reduced. Should the pressure fall below 30 p.s.i., back contact b of Bourdon tube 7 will be closed and intake magnet lLM will be energized over lead 62, causing the pressure to increase. When it is desired to reduce the pressure manually, lever RlMC may be moved to its 0 position, causing relay NPR and consequently exhaust magnet 1X2M to be energized, thus reducing the pressure to the desired value or opening the retarder completely.

The manual operation of the second section of the retarder is similar to that described for the first section. With lever RZMC in its H position, relay ZHPR is picked up and both intake magnets 2I-IM and ZHMM are energized in parallel to bring about a rapid increase in pressure to a relatively high sustained value. When the lever is moved to its L position, the movable contact member of Bourdon tube 10 is energized over leads 51 and 52. Should the pressure increase above 37 p.s.i., front contact a of Bourdon tube 10 will be closed, and relay 20PR will be picked up over its previously traced circuit including back contact 0 of relay 2HPR. Exhaust magnet 2X2M will then be energized, causing the pressure to decrease. Should the pressure fall below 30 p.s.i., back contact b of tube 10 will close, causing intake magnet ZLM to be energized over lead 84 and raising the pressure. In the 0 position of lever RZMC, relay ZOPR will be picked up, exhaust magnet 2X2M will be energized, and the pressure will then be reduced, or the retarder opened completely, as is desired.

With no cars occupying the group retarder, and before any weight information has been registered in relays RL1 and RHI, if the retarder is set for automatic operation by placing levers RIMC and RZMC in their automatic or A positions, both sections of the retarder will be maintained at a standby pressure. Under these conditions, relay AP will be energized over the A contactor of the levers as previously described.

In the first section of the group retarder, the standby pressure is controlled between and 82 p.s.i. by the action of Bourdon tube 6. The movable contact of this Bourdon tube is energized over a previously traced circuit including back contact 0 of relay RlTPP, lead 33, front contact e of relay AP, lead 34, the back point of contact 1 of relay RBI and the back point of contact 1 of relay RL1 in series, and lead 44. Should the pressure increase above 82 p.s.i., front contact a of tube 6 will close and relay IGPR will be energized over lead 36 and back contact c of relay IHPR, causing magnet 1X2M to be energized over the front point of contact b of relay 10PR and lead 69, and the pressure will thereby be reduced. Should the pressure fall below 75 p.s.i., back contact b of Bourdon tube 6 will close, causing intake magnet IHMM to be energized over leads 59 and 60 until the pressure is increased above 75 p.s.i.

In the second section of the group retarder, standby pressure is established between 63 and 70 p.s.i. by

Bourdon tube 11. The movable contact of this Bourdon tube is energized over a previously traced circuit which extends from terminal B of the battery over front contact (1 of relay AP, lead 45, back contacts d of relays RH2 and RLZ in series, lead 47, back contact of relay IVPR, and over lead 82. to the movable contact of Bourdon tube 11. When the pressure rises above 70 p.s.i., front contact a of Bourdon tube 11 is closed, and relay NPR will be energized over lead 50 and back contact 0 of relay ZHPR. Exhaust magnet ZXZM will then be energized over the front point of-contact a of relay ZQPR and lead 9% to reduce the pressure. Should the pressure fall below 63 p.s.i., back contact b of tube 11 will be closed, and magnet ZHMM will be energized over leads 83 and 80 to restore the pressure to the desired range.

Once the weight of an approaching cut is registered in relays RLl and RHl, and before section l-ZGRIT is occupied, in the automatic operation of my equipment the group retarder will be preset to a pressure value in accordance with the weight of the cut.

For light cars, the pressure in the first section is preset between 15 and 22 p.s.i. by the action of Bourdon tube 3. The movable contact of this Bourdon tube will be energized over a previously traced circuit including back contact c of relay RlTPP, lead 33, front contact e of relay AP, lead 34, the back point of contact of relay RHI, the front point of contact 1 of relay RLI, and lead 35. Should the pressure rise above 22 p.s.i., relay NPR will be energized over its previously traced circuit including front contact a of Bourdon tube 8, lead 36, and back con tact c of relay IHPR. Exhaust magnet 1X2M will then be energized over the front point of contact b of relay NPR and lead v69 to reduce the pressure. Should the pressure fall below 15 p.s.i., back contact b of Bourdon tube 8 will close, and intake magnet ILM will be energized over lead 62 to restore the pressure to the desired range. a

For medium weight cars, when relays RL-1 and *RHl are both picked up, the pressure in the firs-t section is preset between and 37 p.s.i. by the action of Bourdon tube 7. The movable contact of this Bourdon tube is energized at this time over a circuit including back contact c of relay RlTPP, lead 33, front contact 2 of relay AP, lead 34, the front point of contact 1 of relay RHl, the front point of contact g of relay RLl, and leads 4.3 and 37. Should the pressure rise above 37 p.s.i., front contact a of tube 7 will be closed, and relay 10PR will be energized over its previously traced circuit, causing exhaust magnet 1X2M to be energized and reduce the pressure. Should the pressure fall below 30 p.s.i., mag net ILM will be energized to restore it to the desired range.

For heavy cars, relay RHI is energized, relay RLl is released, and the pressure in the first section is preset between 75 and 82 p.s.i. by the action of Bourdon tube 6. The movable contact of this Bourdon tube is energized over a previously traced circuit including back contact c of relay RlTPP, lead 33, front contact e of relay AP, lead 34, the front point .of contact 1 of relay RH the back point of contact g of relay RLl, and lead 44. Should the pressure then rise above 82 p.s.i., relay IOPR will be energized over its previously traced circuit and exhaust magnet 1X2M will accordingly be energized to reduce the pressure to the desired range. Should the pressure fall below 75 p.s.i., magnet IHMM will be energized over back contact b of Bourdon tube 6 to increase the pressure to its desired range.

The second section of the group retarder is preset to a range of between 30 and 37 p.s.i. when the pressure in the first section is below p.s.i. At such times, the movable contact of Bourdon tube 5 in the first section is energized lover a previously traced circuit including front contact a of relay AP, lead 45, back contacts d of relays RLZ and RH2 in series, and lead 46. With the pressure in the first section below 35 p.s.i., back contact b of Bourdon tube 5 is closed, and the movable contact of Bourdon tube 16 will be energized over a circuit extending from back contact b of tube 5 over lead 49, front contact b of relay IVPR, which will now be picked up, and leads 53 and 52. Should the pressure in the second section increase above 37 p.s.i., front contact a of Bourdon tube 10 will close which will cause relay NPR to be picked up. Exhaust magnet 2X2M Will then be picked up over the front point of contact a of relay NPR and the pressure will be reduced. Should the pressure in the second section drop below 30 p.s.i., back contact 12 of Bourdon tube 10 will be closed, and intake magnet 2LM Will be energized to increase the pressure.

With the movable contact of Bourdon tube 5 in the first section energized as just described, should the pressure in the first section be above p.s.i., magnet ZHM in the second section will be energized over a circuit extending from front contact a of Bourdon tube 5 over lead 48, causing relay lVPR to pick up, thus causing a circuit to be completed from lead 48 over front contact a of relay lVPR and lead 76 to intake magnet ZHM, The pressure will thus be increased to its highest possible value, for example, p.s.i.

When the pressure in the first section is between 35 and 85 p.s.i., the circuits just traced will not be completed. Under these conditions, the second section of the group retarder will be preset between 63 and 70 p.s.i. by the action of Bourdon tube 11. The movable contact of this Bourdon tube is energized at this time over a circuit including front contact d of relay AP, lead 45, back contacts d of relays RLZ and RH2 in series, lead 47, back contact c of relay lVPR, and lead 82. Should the pressure rise above 70 p.s.i., front contact a of tube 11 will be closed, causing relay NPR to be picked up and exhaust magnet ZXZM to be energized over the circuits previously described. Should the pressure fall below 63 p.s.i., back contact b of tube 11 will be closed, and intake magnet ZHMM will be energized'to increase the pressure to the desired range.

The operation of the group retarder to control -a light weight cut will now be described. It will be assumed that both sections of the retarderare in their automatic condition with levers RlMC and R2MC set to their automatic or A positions. Relay AP will accordingly be energized. It will be further assumed that the out has moved over the hump through approach track section AT, the two sections of the master retarder, and detector track sections 18T and 1-4T with switches 1-8W and 1-4W in their normal positions, and is occupying track section 1-2AT. It will be further assumed that weighrail contactor WRC has functioned to transfer the weight of the cut to the weight coding, storage, and transfer circuits, as described in the above-mentioned copending.

application, and that relay 1-2ALP is now energized and relay l-ZAHP is released. It will be further assumed that V3 computer 2, FIG. 1b, has functioned to supply a proper leaving speed voltage between its output lead 3 and its grounded lead 4, which is supplied to input terminal a of storage unit I-ZGRL-ESU over front contact a of relay 1-2ATP.

With the cut occupying track section 12AT, track relay 1-2ATR will be released and repeater relay 1-2ATP will be picked up.

The output of V3 computer 2 will now be supplied to input terminal a of storage unit 1-2GR1-ESU over lead 3 and front contact a of relay 1-2ATP. At the same time, relay RLl will be picked up over its previously traced circuit including front contact a of relay 1-2ALP, lead 28, front contact 0 of relay 1-2ATP and back contact c of relay GAEC. The circuit for relay RI-Il will be interrupted at the open front point of contact a of relay 1-2AHP.

The first section of the group retarder will now be preset, as previously described, between a pressure of 15 and 22 p.s.i., so that back contact b of Bourdon tube 5 will be closed. The second section of the group reif tarder will accordingly be maintained at a preset pressure of between 30 and 37 p.s.i. by the action of Bourdon tube 10, as previously described.

As the cut moves into section 1-2GR1T, track relay RlTR will be released and repeater relays R1TP and RITPP will be picked up. The output of velocity meter 15 appearing at its output terminal a will now be connected to input terminal b of speed control unit 13 over front contact b of relay RITP. The desired speed storage in unit 1-2GR1-ESU Will be made final when relay RlH is picked up over front contact d of relay RlTP.

The output from terminal of storage unit 12GR1- ESU will now be connected to terminal a of speed control unit 13 over front contact c of relay R1TP. The speed control unit will then begin to function as described in the above-mentioned copending application to compare the measured speed with the selected speed and, when required, energize either its intake terminal e or its exhaust terminals 1 and g.

With relay RlTPP picked up, the previously described circuit for presetting the first section of the retarder will be interrupted at the open back point of contact 0 of relay RITPP. The retarder will now be controlled from terminals 2, f and g of speed control unit 13.

' When terminal 0 of speed control unit 13 is energized, the movable element of Bourdon tube 7 will be energized over the previously traced circuit extending from terminal e of speed control unit 13 and including leads 38 and 39, front contact I; of relay RlTPP, lead 41, front contact c of relay AP, lead 42, the back point of contact e of relay RH1, the front contact 11 of relay RL1, and leads 43 and 37. Under the initial conditions previously described, with the retarder preset between 15 and 22 p.s.i., back contact b of Bourdon tube 7 will be closed. Accordingly, intake magnet lLM will be energized over lead 62, and the pressure will be increased. When the pressure exceeds p.s.i., back contact b of tube 7 will be opened. Should the pressure exceed 37 p.s.i., front contact a of tube 7 will be closed. Relay NPR will then be picked up over lead 36 and back contact c of relay IHPR. Exhaust magnet llXZM will then be energized over the front point of contact b of relay NPR and lead 69 until the pressure is reduced below 37 p.s.i.

Should the speed of the cut decrease below the desired value, terminals 7 and g of speed control unit 13 will be energized. Exhaust magnet 1X1M will then be energized over its previously traced circuit extending from terminal 1 of speed control unit 13 over leads 63 and 64, front contact a of relay AP, lead 66, front contact b of relay RL1, lead 67, back contact a of relay lltlPR, lead 68, and through the Winding of magnet 1X1M to terminal N of the battery. The valve controlled by magnet lXlM will respond quite rapidly, causing a relatively slight decrease in braking which will rapidly be reflected in the higher time derivatives of the speed of the cut, to prevent overcorrection, and consequent hunting of the system. Exhaust magnet 1X2M will be energized from terminal 3 of speed control unit 13 over leads 70 and 72, front contact b of relay AP, lead 73, front contact i of relay RL1, lead 74, the back point of contact b of relay NPR, and lead 69. The valve controlled by this magnet, when opened, will provide a large exhaust capacity if still needed to reduce the combined speed characteristics of the cut.

While section 1-2GR1T is occupied, and before section 1-2GR2T becomes occupied, terminal a of storage unit 12GR2ESU is energized from terminal 0 of storage unit 1-2GR1-ESU over lead 96 and back contact 11 of relay RZTP to transfer the desired speed to the second section storage unit.

As the cut moves into section 1-2GR2T, track relay R2TR will be released and relay RZTP will pick up. Relay 12RC will now be picked up over its previously traced circuit including front contact b of relay RZTP, lead 24, the winding of relay 1-2RC, and back contact d of relay R1EC. The desired speed storage in unit 12GR2-ESU will be made final, since relay RZH will be picked up over front contact g of relay R2TP.

With relay 1-2RC picked up, the previously traced circuit from output terminal 0 of storage unit 12GR1ESU to input terminal a of storage unit 1-2GR2-ESU is interrupted at the open back point of contact 11 of relay RZTP.

At the same time, the output appearing at terminal a of radar velocity meter 16 will be connected to input terminal B of the speed control unit 14 over front contact e of relay RZTP. The output appearing at terminal c of storage unit 1-2GR2-ESU will be applied to input terminal a of speed control unit 14- over front contact 1 of relay 1-2R2TR. Speed control unit 14 will now begin to follow the action of the cut, but will not yet exert any influence on the retarder.

With relay 1-2RC picked up, the weight information stored in relays RL1 and RH1 will be transferred to relays RLZ and RH2 by their previously described circuits. That is, relay RL2 will be picked up over front contact b of relay 1-2RC, front contact c of relay RL1 and lead 30. The pickup circuit for relay RH2 will be interrupted at the open front point of contact 0 of relay RH1.

During the joint occupancy of sections 1-2GR1T and 1-2GR2T, the second section pressure control unit 1-2GR1 is controlled from first section speed control unit 13. Should terminal e of speed control unit 13 be energized, the movable contact of Bourdon tube 10 will be energized over a circuit including leads 38 and 40, the front point of contact a of relay 1-2RC, lead 55, front contact h of relay AP, lead 56, the back point of contact 0 of relay RH2, front contact b of relay RL2, and leads 54, 51 and 52. The action of this tube will maintain the pressure between 30 and 37 p.s.i. while terminal e of speed control unit 1-3 is energized. Should the pressure exceed 37 p.s.i., relay ZQPR and exhaust magnet 2X2M will be energized, as previously described, to reduce the pressure. Should the pressure go below 30 p.s.i., back contact b of tube 10 will be closed and intake magnet ZLM will be energized.

If terminals f and g of speed control unit 13 are energized, exhaust magnets 2X2M and 2X1M will be energized over their previously traced circuits including front contacts e and f of relay 1-2RC, and the pressure will be decreased to the extent necessary to restore the speed characteristics of the cut to the desired value.

When the cut clears section 1-2AT, track relay 1-2ATR will be energized and relay 1-2ATP will be released. The V3 voltage supplied from computer 2 to storage unit 1-2GR1-ESU will now be interrupted at the open front point of contact a of relay 1-2TP. However, the stored voltage will remain in the unit under the control of relay RlH, which is energized over front contact d of relay RlTP. The energizing circuits for relays RL1 and RH1 will now be interrupted at the open front points of contacts b and c of relay 1-2ATP. However, relay RL1 will be held up at this time over its previously traced stick circuit including front contact 2 of relay RlTP and its own front contact a.

With relay 1-2ATP released, relay GAEC will now pick up over its previously traced circuit including back contact d of relay 1-2ATP, front contact f of relay RlTP, and back contact 0 of relay RlEC. The opening of back contacts 0 and d of relay GAEC thus provides further check on the interruption of the transfer circuits from unit 1 to relays RL1 and RH1, but this will obviously have no effect on these relays at this time since their pickup circuits are already interrupted and the stick circuit for relay RL1 is already established.

As the cut clears section 1-2GR1T, track relay RITR will be picked up and relay RlTP will be released. Relay RlTPP will be held up briefly over its stick circuit including back contact b of relay RlEC and its own front contact :1. Relay RlEC will now be picked up over its 21 7 previously traced circuit including the back point of contact a of relay RITP, lead 21, front contact aof relay RZTP, lead 22, front contact b of relay GAEC, the winding of relay RIEC, lead 23, and the back point of contact a of relay RZEC. Relay RltTPP will then be released.

With relay Rl EC picked up, relay GAEC will be released at the end of its predetermined time delay period due to the interruption of its stick circuit at the open back point of contact of relay RlEC. At the same time, relay 1-2RC will be released, due to the interruption of its stick circuit at the open back point of contact d of relay RlEC.

With relay RITP released, relay RLl will be released, due to the interruption of its stick circuit at the open front point of contact e of relay RlTP.

The first section of the group retarder will now be restored to its previously described standby condition, in which the pressure is maintained between 75 and 82 p.s.i. by the action of Bourdon tube 6. The second section will now be controlled from its own speed control unit 14. At this time, relay RL2 is held up over its stick circuit including front contact d of relay RZTP and its own front contact a, while relay RH2 remains released.

When the cut enters track section l-2T, track relay 1-2TR will be released. However, no further action will take place at this itme.

The intake control circuit from terminal e of speed control unit 14 extends from terminal a over lead 78, the back point of contact at of relay 1-2RC, lead 55, front contact h of relay AP, lead 56, the back point of contact 0 of relay RH2, front contact b of relay RLZ, and leads 54, 51 and 52 to the movable contact of Bourdon tube 10. As long as terminal e is energized, Bourdon tube will function as previously described to maintain the pressure between 30 and 37 p.s.i. by energizing intake magnet ZLM or relay NPR and exhaust magnet ZXZM, as required. The exhaust control circuit from terminal 1 of speed control unit 14 extends over lead 89, the back point of contact 1 of relay 1-2RC, lead 85, front contact 1 of relay AP, lead 86, front contact 1 of relay RL2, lead 87, back contact b of relay PR, and lead 88 to the wind ing of magnet 2X1M. The exhaust control circuit from terminal g of speed control unit 14 extends over lead 94, the back point of contact e of relay 1-2RC, lead 91, front contact g of relay AP, lead 92, front contact e of relay RLZ, lead 93, the back point of contact a of relay ZtlPR, and lead 90 to magnet ZXZM. Magnets ZXlM and 2X2M will accordingly be energized in parallel to the extent necessary to restore the combined speed characteristics of the cut to the desired value.

When the cut clears section 1-2GR2T, track relay RZTR will be energized and relay RZTP will be released. Relay RZEC will now be picked up over back contact a of track relay 1-2TR, lead 25, the winding of relay RZEC, lead 26, front contact e of relay RlEC, lead 27, and back contact c of relay RZTP.

With relay RZEC energized, the stick circuit for relay RlEC will be interrupted at the open back point of contact a of relay RZEC, and at the end of its predetermined time delay period, relay RlEC will release. With relay RZTP released, speed control unit 14 will be disconnected both from radar velocity meter 16 and storage unit 1-2GR2-ESU. At the same time, relay RZH will be released and the storage in unit 12GR2-ESU will be cancelled. Relay RLZ will now be released due to the interruption of its stick circuit at the open front point of contact d of relay RZTP.

The second section of the retarder will now be returned to its standby condition, in which it is maintained between 63 and 70 p.s.i. by the action of Bourdon tube 11 as previously described.

When the cut clears section 1-QT, track relay =1 2T R will be energized. Relay RZEC will accordingly release and the apparatus will be restored to its initial condition.

The sequence of operations for a medium weight cut is substantially the same as for the light out just described, and accordingly, in considering the operation of such a out, only those circuits which function dilferently will be escribed. It will be initially assumed that both sections of the group retarder are in their standby conditions, with the first section maintained between 75 and 82 p.s.i. by Bourdon tube 6 and the second section held between 63 and 70 p.s.i. by Bourdon tube 111.

It will next be assumed that the weight of an approaching medium weight cut is registered by the energization of both relays RLl and RHl. The first section of the group retard-er will now be preset to a pressure between 30 and 37 psi. by the action of Bourdon tube 7 as previously described. The second section of the retarder will be preset between 30 and 37 p.s.i. by the action of Bourdon tube it) as long as the pressure in the first section remains below 30 p.s.i. so that back contact b of Bourdon tube 5 is closed. However, should the pressure in the [first section rise above 35 p.s.i., the control of the second section will be transferred to Bourdon tube 11, which will then raise the pressure to between 63 and 70 p.s.i.

When the cut enters track section 1-2GR1T, and speed control unit 13 becomes effective to control unit 1-2GR1, the intake control circuit from terminal e of speed control unit 13 will extend over leads 38 and 39, front contact b of relay RETPP, lead t1, front contact 0 of relay AP, lead 42, the front point of contact e of relay RHl, the front point of contact e of relay RDi, and lead 44 to the movable contact of Bourdon tube 6. As previously described, this tube will function to keep the pressure between 75 and 82 p.s.i. by alternately energizing intake magnet EHMM and relay EOPR, the latter controlling exhaust magnet llXZM, as required.

The exhaust control circuit from terminal 1 of speed control unit 13 extends at this time over leads 63 and 64, front cont-act a of relay AP, lead 66, front contacts b of relays RLl and RH'l in multiple, lead 67, back contact a of relay IOPR, and lead 68 to exhaust magnet IX'IM. The exhaust control circuit from terminal g of speed control unit 13 extends over loads 70 and 72, front contact b of relay AP, lead 73, front contact-s i of relay RL]. and g of relay RH]. in multiple, lead 74, the back point of contact b of relay lOP R, and lead 69 to magnet lXZM. Magnets iX lM and lXQM will accordingly be energized in parallel to effect the necessary reduction in raking force.

When the cut occupies both sections 1-2GR1T and fl-ZGRZT, the second section pressure control unit T ZGRZ will be con-trolled from the first section speed control unit 13. The first section has been maintained, as previously described, between 75 and 82 p.s.i. Back contact b of Bourdon tube 5, which opens at pressures above 35 p.s.i., will accordingly be opened and the preset pressure of the second section will have been increased to between 63 and 70 p.s.i. by the action of Bourdon tube i l. At this time, relays R12 and RH2 will be picked up.

A circuit from terminal e of speed control unit 1-3 will now extend over leads 38 and 4th, the front point of con- !tact d of relay 1-2RC, lead 55, front contact 11 of relay A'P, lead 56, the front point of contact 6 of relay RH2, lead $1, the back point of contact b of relay ZHFR, and loads 79 and 80 to intak-emagnet ZHMM. This magnet will cause the pressure to increase to the extent necessary to reduce the speed characteristics of the cut to the desired value. It will be noted that in this case there is no pressure ceiling established, other than the value of the fluid supply pressure.

At this time, exhaust magnets ZX lM and 2X2M will be controlled from terminals and g of speed control unit 1'3 in the same manner as previously described as in the case of a light cut.

When the cut clear-s section I ZGR IT, the first section will return to its standby condition.- The second section will be operated from a second section speed control unit 14. The intake circuit in this case extends from terminal e of speed control unit 14 over lead 78, the back point of contact d of relay I ZRC, lead 55, front contact 11 of relay AP, lead 56, the front point of contact c of relay RHZ, lead 31, the back point of contact b of relay ZHPR, and over leads 79 and 80 to magnet ZHMM. The exhaust circuits are the same as those described for the light weight cut, controlling exhaust magnets ZX lM and ZXZM from terminals 1 and g of speed control unit 14 over the back points of contacts e and f of relay 1-2RC.

When the cut clears section L ZGRZT, the second section will be restored to its standby condition as previously described.

Since the operation of the retarder in braking a heavy cut is substantially the same as for the light and medium weight cuts, only those aspect-s that are different will be described. When a heavy cut is registered in the first section by energizing relay RH} and maintaining relay RL1 released, the previously described preset circuit for heavy cuts will be established, and Bourdon tube 6 will function to maintain the pressure in the first section between 75 and 82 psi With the pressure in the first section in this range, neither of the contacts of Bourdon tube will be closed, and the pressure in the second section will be maintained between 63 and 70 psi. by the action of Bourdon tube 11 as previously described.

When the heavy cut is in the first section under the control of speed control unit 13, the intake control circuit extends from terminal e of unit 13 over leads 38 and 39, front contact b of relay lblTPP, lead 41, front contact 0 of relay AP, lead 42, and thence over two branches. The first extends over the front point of contact e of relay RH'L the back point of contact 2 of relay RL1, lead 61, the back point of contact b of relay IHPR, and over leads 58 and 60 to intake magnet lHMM. T he second branch extends from lead 42 over front contact d of relay RH l,

back contact d of relay RIJl, lead 57, the back point of contact a of relay IHPR and lead 56 to intake magnet IHM. Magnets IHM and lI-IMM will accordingly be energized in parallel to rapidly increase the braking pressure to a high sustained value, limited only by the pressure of the supply source, until speed control terminal e becomes deenergized.

Exhaust terminals 1 and g of speed control unit 13 control exhaust magnets lXlM and IXZM in parallel in the same manner as described for light and medium cuts.

When the cut occupies both sections 1-2GR1T and 1-2GR2T, relay RHZ will be picked up and relay RLZ will remain released. Pressure control unit 1-2GR2 will now be controlled from speed control unit 13. The intake control circuit for this purpose extends from terminal e of speed control unit 13 over leads 38 and 49, the front point of contact a. of relay 1-2RC, lead 55, front contact 11 of relay AP, lead 56, and thence over a pair of paths, a first extending over the front point of contact c of relay RHZ, lead 31, the back point of contact b of relay ZHPR, and over leads 7f and 30 to intake magnet ZHMM, and the second extending from lead 56 over front contact b of relay RH2, back contact c of relay RLZ, lead 77, the back point of contact a of relay ZHPR, and leads 75 and 76 to intake magnet ZHM. Magnets ZHM and 2HMM will accordingly be energized in parallel for as long as required to bring the speed characteristics down to the desired value.

At this time, terminals 1 and g of speed control unit 13 control exhaust magnets ZXIM and ZXZM in parallel, in the same manner as described for light and medium cuts, when required to reduce the amount of applied brakmg.

When the cut clears section l-ZGRIT, the first section is returned to its standby condition. The second section is now controlled by second section speed control unit 14. The intake control circuits in this case extend from terminal e of speed control unit 14 over lead 78, the back point of contact a of relay 12RC, lead 55, front contact 11 of relay AP, lead 56, and thence over 24 two paths to magnets 2HM and ZHMM which are the same as previously traced when describing the control by the first section speed control unit. Magnets ZHM and ZHMM thus continue to be controlled in parallel when increased braking pressure is required.

Exhaust magnets 2X1M and 2X2M are controlled in parallel from terminals 1 and g of speed control unit 14 in the manner previously described for light and medium cuts. When the second section is vacated, it is returned to its standby condition in the manner previously described.

The operation of the circuits of this embodiment of my invention having been described for single cuts under various conditions which are typical of those encountered in practice, the operation of the apparatus for two cuts of different characteristics sequentially occupying the group retarder will now be considered.

Let it be assumed that two outs which will require different leaving speeds V3 and which are of different average weight approach the group retarder separated by a distance greater than the length of the track circuits, and for example, by a distance of feet. It will be assumed that the Weight coding, storage and transfer circuits 1 function in the manner described in the above copending application to register the weight of each cut in terms of the energized or deenergized conditions of relays 1-2ALP and l- ZAHP as each cut occupies approach track section 1-2AT. It will also be assumed that V3 computer 2 supplies the appropriate leaving speed voltage for each cut at this time.

Initially, both of the retarders will be intheir previously described standby conditions. As the first cut occupies section 1-2AT, its weight will be registered in relays RL1 and RH and its selected leaving speed V3 will be supplied to storage unit 1-2GR1-ESU.

When the first cut enters section l-ZGRIT, storage unit 1-2GR1ESU and radar velocity meter 15 will be connected to speed control unit 13 and the cut will be controlled, at a rate depending on its weight, by the action of speed control unit 13 on retarder control 1-2GR1 as previously described.

When the first cut clears section 1-2AT, both V3 computer 2 and weight unit 1 will be disconnected and will become available to handle information relating to the second cut. The weight storage in relays RL1 and RHl will be maintained over their stick circuits including front contact e of relay RlTP. The leaving speed stored in unit 1-2GR1ESU will be retained, due to the energization of relay RlI-I over front contact d of relay RITP.

When the first cut enters section 1-2GR2T, relay 12RC will pick up and the weight information stored in relays RL1 and RHI will be transferred to relays RLZ and RH2. The storage of the desired leaving speed for the first cut will have been made in storage unit 1-2GR2- ESU and this storage will now be made final by the energization of relay RZH over front contact g of relay R2TP. Radar velocity meter 16 in storage unit 1-2GR2- ESU will now be connected to speed control unit 14, which now commences to follow, but not yet to control, the first cut. The second section pressure control unit Jl-ZGRZ will be operated at this time in response to speed control unit 13 as previously described.

When the first section is vacated by the first cut, it will be restored to its standby condition as previously described, with relay RlH being released due to the opening of its energization circuit at the open front point of contact d of relay RITP, to cancel the leaving speed stored in storage unit 1-2GR1-ESU, and the stick circuits for relays RL1 and RH]. being interrupted at the open front point of contact e of relay RlTP.

With track section l-ZGRIT cleared, relay GAEC will be released as previously described at the end of its predetermined time delay period and will close its back contacts 0 and d. The first section of the group 25 retarder is now in condition to receive information pertaining to the second cut.

When the second cut occupies track section 1-2AT, its leaving speed will be supplied to storage unit l-ZGRI- ESU from V3 computer 2 over front contact a of relay 1-2ATP. At the same time, its weight registration will be transferred from unit 1 over leads 28 and 29, front contacts b and c of relay 1-2ATP.

The first section of the group retarder will now be preset to a pressure in accordance with the weight of the second cut. The second section of the retarder may still be occupied by the first cut, with pressure control unit 12GR2 being controlled by second section speed control unit 14 as previously described.

When the second cut enters section 1-2GR1T, it will be controlled by pressure control unit l-2GRi in lmponse to the act-ion of speed control unit 13 as previously described for a single cut.

When the second sect-ion of the group retarder is vacated by a first out, it will be restored to its standby condition as previously described, the energized combination of relays RLZ and RI-iZ will be released, and relay RZH will be released to clear storage unit 1-2GR2-ESU. At this time, the storage in unit 1-2GR1-ESU will be transferred to unit ll-ZG-RZ-ESU over back contact h of relay RZTP.

The previously described preset circuits for the second section of the retarder will be prepared over back contacts d of relays RLZ and RHZ in series and the second section will follow the first section as previously described. When the pressure in the first section is between 35 and 85 p.s.i., the circuit for this purpose will extend from terminal B of the battery over front contact d of relay AP, lead 45, back contacts d of relays RLZ and RHZ in series, lead 47, back contact of relay llVPR, and lead 82 to the movable contact of Bourdon tube 11. At this time, the movable contact of Bourdon tube 5 will be energized over front contact d of relay AP, lead 45, back contacts a of relays RHZ and RLZ in series, and lead 46. If the control of the second cut in the first section causes the pressure to go below 35 p.s.i., back contact b of Bourdon tube 5 will be closed and the movable element of Bourdon tube will be energized overload 49, front contact b of relay IVPR, and loads 53 and 52. This tube will function as previously described to maintain the pressure in the second section between 30 and 37 psi. On the other hand, if the pressure goes above 85 p.s.i., intake magnet ZHM will be energized over front contact a of Bourdon tube 5, lead 48, front contact a of relay ill/PR, and lead '76.

The further operation of the retarder to control the second out will be the same as that previously described for a single out and will not be repeated. It will be apparent, however, that with the apparatus of my invention, as each location is vacated by a cut, it becomes available for occupancy bya following cut, Which may be independently controlled in accordance with its own measured characteristics.

While I have described only one embodiment of my invention in detail, it will be apparent to those skilled in the art after reading my description that many changes and modifications could be made Within the scope of my invention. Accordingly, I do not wish to be limited to the details shown, but only by the scope of the following claims.

Having thus described my invention, what I claim is:

1. Apparatus for controlling the speed of freight cars traversing a stretch of track, comprising, in combination, a car retarder having a first and a second section located respectively in first and second adjacent track sections in said stretch, means for producing a first signal voltage in accordance with the desired speed of cars leaving said retarder, first speed measuring means for producing a second signal voltage in accordance with the speed of cars occupying said first track section, second speed measuring means for producing a third signal voltage in accordance with the speed of cars occupying said second track section, first speed comparing means for producing a fourth signal voltage in accordance with the difference between said first and second signal voltages, second speed comparing means for producing a fifth signal voltage in accordance with the difference between said first and third signal voltages, means controlled by the occupancy by cars of said first track section for controlling said first retarder section to control the braking force exerted thereby on said cars in accordance with said fourth signal voltage, means controlled by the occupancy by said cars of both said track sections for controlling said second re'tard'er section to control the braking force exerted thereby on the cars in accordance with said fourth signal voltage, and means controlled by the occupancy by said cars of said second track section after the cars have vacated said first track section for controlling said second retarder section to control the braking force exerted thereby on the cars in accordance with said fifth signal voltage.

2. Apparatus for controlling the speed of each cut of cars sequentially occupying first and second sections of a car retarder, comprising, in combination, first speed comparing means for producing a first output voltage in accordance with the difference between the desired speed for each cut when leaving said ret-arder and the speed of such cut in said first section, second speed comparing means for producing a second output voltage in accordance with the difference between said desired speed for each cut and the speed of such cut in said second section, first and second retarder control means for controlling the braking force exerted by said first and second sections respectively, means controlled bythe occupancy by each cut of said first section for controlling said first retarder control means in accordance with said first output voltage produced for such out, means controlled by the joint occupancy by each cut of said first and second sections for controlling said second retarder control means in accordance with said first output voltage produced for such cut; and means controlled by the occupancy by each cut of said second section after such cut has vacated the first section and effective until said second section is vacated by that cut for controlling only said second retarder control means in accordance with said second output voltage.

3. Apparatus of the class described, comprising, in combination, a car retarder having first and second retarder sections located respectively in first and second adjacent track sections in a stretch of track, a first and a second track occupancy detection device for said first and second track sections respectively, each said device operable to a first or second position according as its associated track section is occupied or unoccupied respectively, a first and a second plurality of control devices for said first and second retards-r sections respectively for controlling the braking action of the respective sections, means for producing a first signal voltage representative of a preselected car speed for each car out leaving the retarder, first speed measuring means controlled by said first detection device for measuring the speed of each cut of cars occupying the first retarder section and producing a second signal voltage corresponding to that speed, means for comparing said signal voltages and producing a third signal voltage when the second signal voltage is greater than the first signal voltage and a fourth signal voltage when the second signal voltage is less than the first signal voltage, second speed measuring means controlled by said second detection device for measuring the speed of a cut of cars occupying the second retarder section and producing a fifth signal voltage corresponding to that speed, means for comparing said first and fifth signal voltages and producing a sixth signal voltage when the fifth signal voltage is greater than the first signal voltage and a seventh signal volt-age when the fifth signal voltage is less than the first signal voltage, means controlled by said first detection device when said first detection device occupies its second position for controlling said first plurality of control devices in accordance with said third and fourth signal voltages, means controlled by both said detection devices for controlling said second plurality of control devices in accordance with said third and fourth signal voltages when both said detection devices occupy their second positions, and means controlled by said second detection device for controlling said second plurality of control devices in accordance with said sixth and seventh signal voltages when said second detection device occupies its second position and said first detection device returns to its first position after an operation to its second position.

4. Apparatus for controlling the braking force of each section of independently operable first and second adjacent sections of a railway car retarder, comprising, in combination, means for generating a first voltage representative of a desired leaving speed for a car from the retarder, means for establishing a weight classification for the car as the car approaches the retarder, means for Presetting the potential braking force of both sections of the retarder in accordance with the established weight classification for the car, means for generating a second voltage representative of the speed of the car in the first section of the retarder, means for comparing the first and second voltages and deriving a resultant third voltage representative of the difference between the first and second voltages, means for superseding said preset braking force of the first and second sections of the retarder and controlling the braking force of the sections in accordance with said third voltage, means for generating a fourth voltage repre sentative of the speed of the car in the second section of the retarder, means for comparing the first and fourth voltages and deriving a resultant fifth voltage representative of the difference between the first and fourth voltages, and means for controlling the braking force of the second section in accordance with said fifth voltage when the car vacates the first section.

' 5. Apparatus for at times jointly and at other times independently controlling the braking action of motor actuated first and second adjacent sections of a car retarder having an approach track section in approach thereto, comprising, in combination; first, second, and third occupancy detectors for said first section, the second section and said approach track section respectively; means for measuring the weight of each cut of cars approaching the retarder, means controlled by the third occupancy detector and the weight measuring means for registering a weight classification for each cut when the cut occupies the approach track section, means for generating a first signal voltage representative of the desired leaving speed of each cut from the retarder, first speed measuring means for said first section controlled by the movement of each cut through that section for generating a second signal voltage representative of the speed of the cut in the section, second speed measuring means for said second section controlled by the movement of each cut through that section for generating a third signal voltage representative of the speed of the cut in the section, a first and a second voltage comparing device for said first and second sections, respectively, means controlled by the first occupancy detector for supplying said first and second signal voltages for each cut to said first voltage comparing device when the cut occupies said first section, means controlled by the second occupancy detector for supplying said first and third signal voltages for each cut to said second voltage comparing device when the cut occupies said second section, a plurality of actuating motor control devices for each section of the retarder, means controlled by said weight registering means and said third occupancy detector for controlling the motor control devices for both sections of the retarder in accordance with the weight classification for a first cut approaching the retarder, means controlled by said first voltage comparing device for deriving a fourth signal voltage representative of the difference between said first and second signal voltages when the signals are supplied to that device, means controlled by said first voltage comparing device for controlling the motor control devices for both sections of the retarder in accordance with said fourth signal voltage, means controlled by said second voltage comparing device for deriving a fifth signal voltage representative of the dilference between said first and third signal voltages when the signals are supplied to that device, and means controlled by said second voltage comparing device and said first and second occupancy detectors for controlling the motor control devices for the second section of the retarder in accordance with said fifth signal voltage when said first cut occupies only the second retarder section.

6. Control apparatus for a motor actuated car retarder having first and second independently operable sections, comprising, in combination, first and second speed measuring devices for said first and second sections respectively, first and second speed comparing devices for said first and second sections respectively, first and second occupancy detector devices for said first and second sections respectively, means controlled by the three socalled first devices for producing a first output voltage representative of the difference between the speed of a cut of cars when occupying the first section and a desired leaving speed for the cut from the retarder, means controlled by the three so-called second devices for producing a second output voltage representative of the difference between the speed of said cut of cars when occupying the second section and said desired speed, a first and a second plurality of motor control devices for said first and second sections respectively, means controlled by said first output voltage for selectively controlling said first plurality of motor control devices, means controlled by said first output voltage and said occupancy detector devices for selectively controlling said second plurality of motor control devices when said cut of cars occupies both said sections, and means controlled by said second output voltage and said occupancy detector devices for selectively controlling said second plurality of motor control devices when said cut occupies said second section only subsequent to its said occupancy of both said sections.

7. Freight car braking means, comprising in combination, a motor actuated car retarder having first and second sections located on first and second adjacent track sections respectively, a first and a second occupancy relay for said first and second track sections respectively and each actuated from a first position to a second position when its respective track section is occupied by a cut of cars, first voltage generating means controlled by said first occupancy relay in its second position and the speed of a cut of cars occupying the first retarder section for generating first output voltages corresponding to variations of the speed of that cut from a predetermined speed, second voltage generating means controlled by said second occupancy relay in its second position and the speed of a cut of cars occupying the second retarder section for generating second output voltages corresponding to variations of the speed of that cut from a predetermined speed, a plurality of motor control devices for each retarder section, means controlled by the first track occupancy relay in its second position for supplying said first output voltages to said motor control devices for the first retarder section, means controlled by both track occupancy relays for supplying said first output voltages to said motor control devices for the second retarder section when both track sections are occupied by the same cut of cars, and means controlled by both track occupancy relays for supplying said second output voltages to said motor control devices for the second retarder section when the second track section only is occupied by a cut of cars or when the first and second track sections are each occupied by a separate cut of cars.

8. In a system for automatically controlling the braking action of a two section car retarder in a classification 

2. APPARATUS FOR CONTROLLING THE SPEED OF EACH CUT OF CARS SEQUENTIALLY OCCUPYING FIRST AND SECOND SECTIONS OF A CAR RETARDER, COMPRISING, IN COMBINATION, FIRST SPEED COMPARING MEANS FOR PRODUCING A FIRST OUTPUT VOLTAGE IN ACCORDANCE WITH THE DIFFERENCE BETWEEN THE DESIRED SPEED FOR EACH CUT WHEN LEAVING SAID RETARDER AND THE SPEED OF SUCH CUT IN SID FIRST SECTION, SECOND SPEED COMPRISING MEANS FOR PRODUCING A SECOND OUTPUT VOLTAGE IN ACCORDANCE WITH THE DIFFERENCE BETWEEN SAID DESIRED SPEED FOR EACH CUT AND THE SPEED OF SUCH CUT IN SAID SECOND SECTION, FIRST AND SECOND RETARDER CONTROL MEANS FOR CONTROLLING THE BRAKING FORCE EXERTED BY SAID FIRST AND SECOND SECTIONS RESPECTIVELY, MEANS CONTROLLED BY THE OCCUPANCY BY EACH CUT OF SAID FIRST SECTION FOR CONTROLLING SAID FIRST RETARDER CONTROL MEANS IN ACCORDANCE WITH SAID FIRST OUTPUT VOLTAGE PRODUCED FOR SUCH CUT, MEANS CONTROLLED BY THE JOINT OCCUPANCY BY EACH CUT OF SAID FIRST AND SECOND SECTIONS FOR CONTROLLING SAID SECOND RETARDER CONTROL MEANS IN ACCORDANCE WITH SAID FIRST OUTPUT VOLTAGE PRODUCED FOR SUCH CUT; AND MEANS CONTROLLED BY THE OCCUPANCY BY 